A futuristic "plasma jet" that eradicates tooth decay without fillings could be replacing the dentist's drill in as little as three years, a study claims.

The space-age device fires a beam of electrically charged oxygen atoms into tooth cavities to obliterate decay-causing bacteria without pain.

The study has shown that firing low-temperature plasma beams at dentine – the fibrous tooth structure below the enamel – can reduce bacteria levels by up to 10,000 times. Plasmas are produced when atoms in a gas are stripped of one or more of their electrons, leaving them positively charged.

Researchers in Germany tested the effectiveness of the plasma jet against common dental bugswhich form film on the surface of teeth and are responsible for the erosion of tooth enamel and dentine that causes cavities. The scientists infected dentine from extracted human molars with four strains of bacteria and exposed it to plasma for between six and 18 seconds. The longer the treatment continued, the greater the amount of bacteria that was eliminated.

Lead researcher Dr Stefan Rupf, from Saarland University in Homburg, said: "The low temperature means they can kill the microbes while preserving the tooth. Presently, there is huge progress being made in the field of plasma medicine and a clinical treatment for dental cavities can be expected within three to five years."